Self-synchronizing load lifting and lowering system for straddle carriers and the like



y 7, 1968 R. o. GORDON SELF-SYNCHRONIZING LOAD LIFTING AND LOWERING SYSTEM FOR STRADDLE CARRIERS AND THE LIKE 5 Sheets-Sheet 1 Filed July 14, 1966 INVENTOR RICHARD O. GORDON ATTORNEY M y 7, 1968 R. o. GORDON 3,381,833

SELFSYNCHRONIZING LOAD LIFTING AND LOWERING SYSTEM FOR STRADDLE CARRIERS AND THE LIKE Filed July 14, 1966 5 Sheets-Sheet I ELI: l 1 J l l m O \N 9 (9 00 9 0 I (o g g Q\ INVENTOR RICHARD O. GORDON ATTORNEY May 7, 1968 R. o. GORDON 3,381,

SELF-SYNCHRONIZING LOAD LIFTING AND LOWERING SYSTEM FOR STRADDLE CARRIERS AND THE LIKE Filed July 14, 1966 3 Sheets-Sheet 5 FIG. 3

I02 98 88 H4 H6 INVENTOR RICHARD o. GORDON ATTORNEY Unite This invention relates to load elevating systems, and more particularly to self-synchronizing fluid systems that are especially suitable for straddle carriers and the like.

In elevating systems having a plurality of fluid motors there is often a problem of keeping the motors in synchronization because generally the load being lifted is not uniformly distributed. One approach to keeping the fluid motors in synchronization is to supply fluid to them through a flow divider having one outlet for each motor. Theoretically, this should keep the motors in synchronization; however, it has been found that where heavy loads are involved, for example, 50,000 pounds, that there is sufficient leakage in the flow divider and the motors so that even though a flow divider is being used the motors will tend to get out of synchronization with the consequent binding of various parts of the lifting mechanism which may result in faulty operation and even damage to the system. Consequently, a principal object of my invention is to provide a load lifting and lowering system in which movement of the fluid motors is self-synchronizing.

In carrying out my invention in a preferred embodirnent thereof I provide four double-acting extensible fluid motors which are attached to the load engaging means and the vehicle frame. A separate source of pressurized fluid is provided for each fluid motor. In conjunction with each fluid motor there is provided a motor control and synchronizing valve which is operable to direct pressurized fluid to the associated motor to cause it to extend or retract or block communication with the associated fluid motor. Means is provided for actuating each valve to control raising or lowering of the load engaging means, and follow-up means is provided between each valve and the associated fluid motor so that movement of any fluid motor tends to cause the associated valve to return to its fluid communication blocking position.

The above and other objects, features and advantages of my invention will be more readily understood by persons skilled in the art when the following detailed description is taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a perspective view of a straddle carrier embodying my invention,

FIGURE 2 is a partially diagrammatic and partially schematic view showing to advantage the fluid circuitry associated with my invention and FIGURE 3 is an enlarged fragmentary view, partially in cross section, showing in detail a motor control and synchronizing valve and the valve actuator motor associated therewith.

Referring now to the drawing, the reference numeral iii denotes generally a straddle carrier which has an elongated and inverted U-s'naped frame 12 which defines a bay within which loads may be carried. Frame 12 is supported at each front corner thereof by a pair of drive wheels 14, only one of which can be seen, and at the rear corners thereof by a pair of dirigible wheels 16-. Attached to the top of frame 12 and extending forwardly thereof is an operators cab 13 in which an operator sits and which is provided with all the necessary controls for operating carrier 10.

Disposed within the bay formed by frame 12 is a pair States Patent ice of longitudinally extending and laterally spaced apart generally -L-shaped rails 20 and 22 which serve as load engaging means.

The rails 2t and 22 are part of a self-synchronizing load lifting and lowering system which, in addition, includes four load lifting mechanisms 24, 26, 28 and 30 and operator-controlled means for simultaneously actuating the mechanisms to raise or lower rails 20 and 22.

Since all of the lifting mechanisms are identical, only mechanism 24 will be explained in detail, like reference numerals being applied to all of the mechanisms. Mechanism 24 includes a double-acting fluid motor 32, a motor control and synchronizing valve 34, a valve actuating motor 36, a source of pressurized fluid or pump 38 and a bell crank 40.

Fluid motor 32 includes a cylinder 42 which has the head end thereof connected to rail 26. Slidably disposed in cylinder 42 is a piston 44 to which a piston rod 4:? is connected. Piston rod 46 extends outwardly through the rod end of cylinder 42 and is connected to the upper part of frame 12.

Referring now especially to FIG. 3, valve 34 includes an elongated body 48 with a longitudinally extending bore 50 therein. Three longitudinally spaced apart annular grooves 52, 54 and 56 are located in the wall of bore 50. Communicating with groove 54 is an inlet port 58. Communicating with groove 56 is an outlet port 60 which also communicates with groove 52 via a connecting passage 62. A first fluid motor port 64 and a second fluid motor port 66 communicate with bore 50. A conduit connects motor port 64 with the rod end of the interior of cylinder 42 and a conduit 67 connects motor port 66 with the head end of the interior of cylinder 42.

Slidably disposed in bore St) is a spool 68. Spool 68 includes three longitudinally spaced apart lands 70, 72 and 74 thereon. An annular groove 76 is cut in land 70, a pair of annular grooves 78 and 80 are cut in land 72 and an annular groove 82 is cut in land 74. Disposed in spool 68 and communicating groove 76 wit-h groove 7 8 is a fiuid passage 84. Also disposed in spool 68 is a fluid passage 86 which communicates groove 80 with groove 32.

It will now be evident that valve 34 is a four-way open center valve with closed motor ports. Thus, with the spool and body in the position shown in FIG. 3, motor ports 64 and 56 are blocked from fluid communication with inlet port 53 and outlet port 6d and with each other while at the same time inlet port 53 is in fluid communication with outlet port 60 by way of passages 84 and 86. By shifting body 48 toward the right, as viewed in FIG. 3, inlet port 58 is placed in fluid communication with motor port 6e while motor port 64 is placed in fluid communication with outlet port 60. Shifting body 48 in the opposite direction places inlet port 58 in fluid communication with motor port 64 and at the same time places motor port 66 in fluid communication with outlet port 60.

Still referring to FIG. 3, valve actuating motor 36 includes a cylinder 88 which is connected to valve body 43. Slidably disposed in cylinder 88 is a piston 90. Attached to piston 9% is a piston rod 92 which extends outwardly through cylinder 88. The outer end of piston rod 92 is connected to the bottom of an open-ended cylinder 94 within which cylinder 88 is partially telescoped. Attached to cylinder $8 is a pair of longitudinally spaced apart rings 96 and 9?. Similarly, a pair of rings itlti and 182 are connected to cylinder 94. Disposed inwardly of and adjacent to these rings is a pair of loose rings 104 and 106 which are biased apart by means of a compression spring 108. By virtue of this arrangement of rings and compression spring cylinder 88 is always biased to return to the position shown in FIG. 3.

Cylinder 94, and hence piston 90, is connected to frame 12 by means of a ball and socket joint 110. Like wise, spool 68 is connected to hell crank by means of a ball and socket joint 112.

A first port 114 communicates with the interior of cylinder 88 adjacent the rod end thereof and a second port 116 communicates with the interior of cylinder 88 adjacent the head end thereof so that supplying pressurized fluid to port 114 causes cylinder 88 to move toward the left, as viewed in FIG. 3, and supplying pressurized fluid to port 116 causes cylinder 88 to move toward the right.

Referring now specifically to FIG. 2, pump 38 draws fluid from a fluid reservoir 118 via a conduit 120 and supplies pressurized fluid to the inlet port 58 of valve 34 via a conduit 122. Also connected to conduit 122 is a pressure relief valve 124 which vents back to reservoir 118. A conduit 126 connects outlet port 60 of valve 34 with reservoir 118.

Bell crank 48 is pivotally connected to frame 12 at 126 and includes a leg 128 connected to ball and socket joint 112 and hence spool 68 of valve 34 and an extensible leg 130 with a fixed portion 132 and a movable portion 134 slidably telescoped within portion 132. Movable portion 134 has the outer end thereof pivotally connected to cylinder 42 by means of a pin and bracket connection 136.

The means for simultaneously actuating the valves 34 includes a charging pump 142 and a four-way open center valve 138 which serves as a main control valve and is operated by a control handle 140 connected thereto.

Valve 138 includes an inlet port 144, an outlet port 146, a first port 148 and a second port 150. The operation of valve 138 is exactly the same as that of valve 34. That is, when the valve is in a first position ports 148 and are blocked from fluid communication with each other and with inlet port 144 and outlet port 146. Actuation of valve 138 to a second position places port 148 in fluid communication with inlet port 144 and at the same time places port 150 in communication with outlet port 146. Similarly, actuation of valve 138 to a third position places port 150- in fluid communication with inlet port 144 and at the same time places port 148 in fluid communication with outlet port 145.

Connected to port 148 is a conduit 152 which connects with a pair of branch conduits 154 and 156. Conduit 154 communicates with ports 114 of valve actuating motors 36 on one side of straddle carrier 10 and conduit 156 communicates with ports 114 of valve actuating motors 36 on the other side of straddle carrier 10. Connected to port 150 of valve 138 is a conduit 158 which communicates with a pair of branch conduits 160 and 162. Conduit 160 communicates with ports 116 of valve actuating motors 36 on the one side of straddle carrier 10 and conduit 162 communicates with ports 116 of valve actuating motors 36 on the other side of straddle carrier 10.

Charging pump 42 draws fluid from reservoir 118 via a conduit 164 and supplies pressurized fluid to inlet port 144 of valve 138 via a conduit 166. Disposed in conduit 166 is a fluid pressure relief valve 168 which vents to reservoir 118 via a conduit 170. Outlet port 146 of valve 138 is connected to reservoir 118 by a conduit 172.

In order to enable persons skilled in the art to better understand my invention I will now explain the operation of it.

It will be assumed that the load engaging members or rails 20 and 22 are in the lowered position with a load disposed therebetween, and that it is desired to elevate the load to transport it to a new location with straddle carrier 10. The operator manipulates control handle 140 to actuate valve 138 from the position in which fluid communication with ports 148 and 150 is blocked to a position communicating inlet port 144 with port 148 and at same time connecting outlet port 146 with port 150. With valve 138 in this position pressurized fluid will be supplied to the rod end of the interior of cylinders 88 via conduits 152, 154 and 156. Supplying pressurized fluid to the rod end of the interior of cylinders 82 causes them, together with body 48 of the associated valves 34 to move toward the left, as viewed in FIG. 3, against the bias of compression springs 108. Shifting body 48 of valves 34 in this direction from the position shown in FIG. 3 places motor ports 64 in fluid communication with inlet ports 58 and places motor ports 66 in fluid communication with outlet ports 60. Thus, pressurized fluid from pumps 38 is directed to the rod end of the interior of cylinders 42 of motors 32 via conduits 65. As a result cylinders 42 move vertically upwardly, thereby elevating rails 20 and 22 and the load engaged by the rails. Upward movement of cylinders 42 causes bell cranks 40' to pivot so that spools 68 of valves 34 are shifted back to the relative position with valve body 48 shown in FIG. 3, so that fluid communication between motor ports 64 and 66 with inlet port 58 and outlet port 60 is again blocked. Because movement of spool 68 follows up movement of body 48 of valves 34 through the action of bell cranks 40 it will be seen that there must be continued movement of valve bodies 48 for continued movement of cylinders 42.

If the load being lifted is distributed evenly between the four lifting mechanisms 24, 26, 28 and 30 all of the cylinders 42 will move up evenly. However, generally speaking, the loads that are handled by a straddle carrier are not evenly distributed between the four lifting mechanisms. Assume, for example, that there is a greater load being lifted by mechanisms 26, 28 and 30 than is being lifted by mechanism 24. In this situation there will be a tendency for cylinder 42 of the motor 32 associated with mechanism 24 to move up more rapidly than the cylinders of the other motors 32. As upward movement of the cylinder 42 associated with lifting mechanism 24 begins to get ahead of the other cylinders, the bell crank 40 associated with mechanism 24 is pivoted further so that spool 68 of the associated valve 34 is shifted toward the left, as viewed in FIG. 3, further than the spools of the other valves, whereby the fluid flow being directed to the cylinder 42 associated with lifting mechanism 24 is reduced below that of the fluid flow to the other cylinders, thus permitting the other cylinders to catch up with the cylinder 42 associated with lifting mechanism 24. From what has been described, it will be clear at this point that a different load can be on each load lifting mechanism rather than merely on one and this system will synchronize movement of all the load lifting motors by slowing down the movement of the lift motor or motors which tend to get ahead of the other lift motors.

While only a single preferred embodiment of my invention has been disclosed and described in detail, it will be understood that various modifications and changes can be made to my invention without departing from the scope or spirit thereof. Therefore, the limits of my invention should be determined from the following claims.

I claim:

1. For use with a straddle carrier having a frame and a fluid reservoir, a self-synchronizing load lifting and lowering system comprising:

load engaging means,

a plurality of load lifting mechanisms,

each mechanism including:

a fluid motor connected to the frame and the said load engaging means, the said motor having: a cylinder connected to the said load engaging means, the said cylinder having a head end and a rod end, a piston slidably disposed in the said cylinder and a piston rod connected to the said piston and the frame and extending through the said cylinder rod end,

a motor control and synchronizing valve ineluding:

a body,

a bore in the said body,

inlet, outlet, first and second motor ports disposed in the said body and communicating with the said bore,

the said outlet port being connected to communicate with the fluid reservoir,

the said first motor port being connected to communicate with the said cylinder adjacent the said rod end and the said second motor port being connected to communicate with the said cylinder adjacent the said head end, and

a spool slidably disposed in the said bore the said body and spool being movable relative to each other from a first position in which fluid communication between the said inlet and outlet ports and the said motor ports is blocked to either a second position in which the said inlet port is placed in fluid communication with the said first motor port and the said outlet port is placed in fluid communication with the said second motor port or a third position in which the said inlet port is placed in fluid communication with the said motor port and the said outlet port is placed in fluid communication with the said first motor port,

a valve actuating motor for moving the said valve body between the said first, second and third positions relative to the said spool and includmg:

an elongated cylinder with a head end and a rod end, the said actuating motor cylinder being fixed to the said valve :body,

a first port communicating with the said actuating motor cylinder adjacent the said said rod end thereof and a second port communicating with the said actuating motor cylinder adjacent the said head end thereof,

a piston slidably disposed in the said actuating motor cylinder,

a piston rod connected to the said actuating motor piston and frame and extending through the said actuating motor cylinder rod end, and

spring means connected to the said actuating motor piston rod and cylinder for biasing the said actuating motor cylinder to a predetermined longitudinal position relative to the said actuating motor piston,

means connected to the said motor cylinder and the said valve spool and responsive to movement of the said motor cylinder for moving the said valve spool to the said first position relative to the said body, and

a fluid pump,

the said fluid pump being connected to the said valve inlet port to supply pressurized fluid thereto, and

means for either supplying pressurized fluid to all of the said first ports of the said actuating motors while communicating all of the said second ports of the said actuating motors with the reservoir or supplying pressurized fluid to all of the said second ports of the said actuating motors while communicating all of the said first ports of the said actuating motors with the reservoir.

2. A self-synchronizing load lifting and lowering system as set forth in claim 1 wherein the said pressurized fluid supply means includes:

a charging pump which draws fluid from the reservoir and a main control valve having:

a body, a bore in the said control valve body, inlet, outlet, first and second ports disposed in the said control valve body and communicating with the said control valve bore,

the said control valve inlet port being connected to the said charging pump to receive pressurized fluid therefrom, the said control valve outlet port being connected to communicate with the reservoir, the said first control valve port being connected to communicaate with the said first actuating motor port, and the said second control valve port being connected to communicate with the said second actuating motor port, and a spool slidably disposed in the said control valve bore,

the said control valve body and spool being movable relative to each other from a first position in which fluid communication between the said control valve inlet and outlet ports and the said first and second control valve ports is blocked to either a second position in which the said control valve inlet port is placed in fluid communication with the said first control valve port and the said control valve outlet port is placed in fluid communication with the said second control valve port or a third position in which the said control valve inlet port is placed in fluid communication with the said second control valve port and the said control valve outlet port is placed in fluid communication with the said first control valve port.

3. A self-synchronizing load lifting and lowering system as set forth in claim 1 wherein the said spool moving means includes a bell crank,

the said bell crank having first and second legs and being connected intermediate the legs thereof to the frame for pivotal movement,

the said first leg being pivotally connected to the said motor cylinder and the said second leg being pivotally connected to the said valve spool.

4. A self-synchronizing load lifting and lowering system as set forth in claim 3 wherein the said first leg of the said bell crank includes:

a first member and a second member connected to the said first member and slidable relative thereto so that the length of the said first leg varies as the said motor cylinder moves up or down.

5. A self-synchronizing load lifting and lowering system as set forth in claim 2 wherein the said spool moving means includes a bell crank, the said bell crank having first and second legs and being connected intermediate the legs thereof to the frame for pivotal movement, the said first leg being pivotally connected to the said motor cylinder and the said second leg being pivotally connected to the said valve spool.

6. A self-synchronizing load lifting and lowering system as set forth in claim 2 wherein the said first leg of the said bell crank includes a first member and a second member connected to the said first member and slidable 8 relative thereto so that the length of the said first leg motor port are in fluid communication, varies as the said motor cylinder moves up or down. a valve actuating fluid motor having:

7. For use with a straddle carrier having a frame and a first portion connected to the frame, a fluid reservoir, a self-synchronizing load lifting and lowa second portion operatively connected to the said valve and movable relative to the said first portion, and spring means connected between the said portions for biasing the said second portions to a predetermined position relative to the said first portion, and means connected to the said load lifting motor and the said valve and responsive to actuation of ering system comprising:

load engaging means, a plurality of load lifting mechanisms, each mechanism including:

a retractable load lifting fluid motor connected to the frame and the said load engaging means, 10 a motor control and synchronizing valve having:

a body the said load lifting motor for returning the d? bandouflet port and a motor Port said valve to the said first position thereof,

mt e Sal o a source of pressurized fluid,

the said motor Port being connected in the said source being connected to the said valve fluid communifiation with the sflid inlet port to supply pressurized fluid thereto,

tor and the said outlet port being conand nected in fluid communlcation h the means for supplying pressurized fluid to the said valve said reservoir, and actuating motor to cause the said second portion a spool slidably disposed in the said body so thereof to move.

that the said body and spool are movable relative to each other from a first position References Cited in which fluid communication between the UNITED STATES PATENTS said inlet and outlet ports and the said mo- 5 3 9 tor port is blocked to either a second posi- 10/1967 Burgess et a1 214 394 tion in which the said inlet p and motor GERALD M. FORLENZA, Primary Examiner.

port are in fluid communication or a third position in which the said outlet port and ALBERT I. MAKAY, Assistant Exammer. 

1. FOR USE WITH A STRADDLE CARRIER HAVING A FRAME AND A FLUID RESERVOIR, A SELF-SYNCHRONIZING LOAD LIFTING AND LOWERING SYSTEM COMPRISING: LOAD ENGAGING MEANS, A PLURALITY OF LOAD LIFTING MECHANISMS, EACH MECHANISM INCLUDING: A FLUID MOTOR CONNECTED TO THE FRAME AND THE SAID LOAD ENGAGING MEANS, THE SAID MOTOR HAVING: A CYLINDER CONNECTED TO THE SAID LOAD ENGAGING MEANS, THE SAID CYLINDER HAVING A HEAD END AND A ROD END, A PISTON SLIDABLY DISPOSED IN THE SAID CYLINDER AND A PISTON ROD CONNECTED TO THE SAID PISTON AND THE FRAME AND EXTENDING THROUGH THE SAID CYLINDER ROD END, A MOTOR CONTROL AND SYNCHRONIZING VALVE INCLUDING: A BODY, A BORE IN THE SAID BODY, INLET, OUTLET, FIRST AND SECOND MOTOR PORTS DISPOSED IN THE SAID BODY AND COMMUNICATING WITH THE SAID BORE, THE SAID OUTLET PORT BEING CONNECTED TO COMMUNICATE WITH THE FLUID RESERVOIR, THE SAID FIRST MOTOR PORT BEING CONNECTED TO COMMUNICATE WITH THE SAID CYLINDER ADJACENT THE SAID ROD END AND THE SAID SECOND MOTOR PORT BEING CONNECTED TO COMMUNICATE WITH THE SAID CYLINDER ADJACENT THE SAID HEAD END, AND A SPOOL SLIDABLY DISPOSED IN THE SAID BORE THE SAID BODY AND SPOOL BEING MOVABLE RELATIVE TO EACH OTHER FROM A FIRST POSITION IN WHICH FLUID COMMUNICATION BETWEEN THE SAID INLET AND OUTLET PORTS AND THE SAID MOTOR PORTS IS BLOCKED TO EITHER A SECOND POSITION IN WHICH THE SAID INLET PORT IS PLACED IN FLUID COMMUNICATION WITH THE SAID FIRST MOTOR PORT AND THE SAID OUTLET PORT IS PLACED IN FLUID COMMUNICATION WITH THE SAID SECOND MOTOR PORT OR A THIRD POSITION IN WHICH THE SAID INLET PORT IS PLACED IN FLUID COMMUNICATION WITH THE SAID MOTOR PORT AND THE SAID OUTLET PORT IS PLACED IN FLUID COMMUNICATION WITH THE SAID FIRST MOTOR PORT, A VALVE ACTUATING MOTOR FOR MOVING THE SAID VALVE BODY BETWEEN THE SAID FIRST, SECOND AND THIRD POSITIONS RELATIVE TO THE SAID SPOOL AND INCLUDING: AN ELONGATED CYLINDER WITH A HEAD END AND A ROD END, THE SAID ACTUATING MOTOR CYLINDER BEING FIXED TO THE SAID VALVE BODY, A FIRST PORT COMMUNICATING WITH THE SAID ACTUATING MOTOR CYLINDER ADJACENT THE SAID SAID ROD END THEREOF AND A SECOND PORT COMMUNICATING WITH THE SAID ACTUATING MOTOR CYLINDER ADJACENT THE SAID HEAD END THEREOF, A PISTON SLIDABLY DISPOSED IN THE SAID ACTUATING MOTOR CYLINDER, 